MoS2 negative capacitance FETs with CMOS-compatible hafnium zirconium oxide
The attractiveness of negative capacitance field-effect transistors (NC-FETs) stems from their ability to enable a subthreshold swing (SS) below the 60 mV/decade thermal limit at room temperature - a direct effect of the step-up voltage amplifier behavior of the ferroelectric [1]. This effect has been shown to yield sub-60 mV/dec SS in several Si-based NC-FETs [2-4]; however, as Si-based devices become increasingly difficult to scale, it is pertinent to explore alternative materials for NC-FETs that offer scalability in voltage as well as size [5]. One promising alternative channel material is the 2D transition metal dichalcogenide (TMD, such as MoS2), which offer sub-nm thinness and a more stable channel capacitance that, when coupled with the NC-effect, could produce steep switching over a broad range of current. To date, the only demonstration of an NC-FET with a 2D channel used a polymeric ferroelectric, resulting in a lack of stability and CMOS-compatibility despite superb low-voltage switching [6]. In this work, we demonstrate 2D NC-FETs using MoS2 with CMOS-compatible hafnium zirconium oxide (HfZrO2 or HZO) as the ferroelectric to achieve repeatable and sustained sub-60 mV/dec switching.
